Conventional roller shutters are designed to provide security from break-ins or protection from storms. Because such protection and security may not always be necessary or desired, such as during the day when a retail store is open for business or during fine weather when a homeowner wishes to open windows or enjoy an ocean view, roller shutters are designed to be retractable into a casing in which they are stored. In some examples, to facilitate compact storage, the rigid shutter slats that are designed to resist hurricane winds and burglars also must be capable of conforming to a roll.
One conventional shutter slat is made to conform to a roll by providing a loose articulation between slats. Slats are slidably engaged at the upper edge of one slat and the lower edge of another slat. The upper edge comprises a vertical projection terminating in a hook-shaped profile. The lower edge comprises a first portion and a second portion that cooperate to define a vertical pocket. The hook-shaped profile of the upper edge allows the upper edge to engage the first portion of the lower edge, also having a hook-shaped profile. The upper edge is prevented from undesirably disengaging the lower edge by the second portion of the lower edge, which comprises a guard extending downward to slightly below the hook-shaped profile of the lower edge, defining a horizontal aperture between the first and second portions of the lower edge. The vertical pocket defined by the first and second portions of the lower edge is similar in depth to the height of the vertical projection of the upper edge. This shutter configuration's flexibility arises from the pivoting of the vertical portion of the upper edge within the horizontal aperture.
One result of this configuration is that the upper edge has significant vertical clearance within the vertical pocket. Shutters according to this configuration are known to have a clearance up to one-quarter inch per slat, or even more. A shutter having 48 slats and one-quarter inch clearance per slat would then have a total clearance of twelve inches between the fully open and fully closed positions. To raise such a shutter having a torsion spring as a counterbalance, a user must lift the bottom slat either by hand or mechanically to correct for the full amount of clearance before the shutter will begin to retract. In such a shutter, a user would have to lift approximately 150 pounds by twelve inches in order to engage the shutter's retraction mechanism. Shutters of this configuration do not obtain full benefit of the counterbalance, as provided by the torsion spring or by other means.
A further result of this configuration is that the loosely articulated slats are known to be noisy. The slats rattle against each other during extension and retraction. In addition, when the roller shutter is deployed, the normal forces of the wind are sufficient to cause the slats to rattle audibly.
Conventional shutter slats are generally designed to hang from a roll or spindle, the roll or spindle contained in a casing. When the shutter is retracted, the slats wrap around the spindle. Because the slats do not fit together compactly around the roll, the resulting shutter assembly, when retracted, creates a roll with a large diameter, and therefore requires a large casing for the roll. This can be unsightly, especially in shutter applications used on residential buildings. Thus, a shutter assembly that is capable of compact storage is desirable.
One solution to the problem of compact storage includes the use of slats that are sized to fit snugly against each other, as described in U.S. Pat. No. 7,409,980 to Heissenberg, titled “Rolling Shutter Assembly.” The slats in this configuration are substantially similar to the slats described in U.S. Pat. No. 6,095,225 to Miller. However, the slats are dimensioned such that the heights of the slats increase as the slats lie further away from the spindle at the center of the shutter. This configuration allows the slats to fit together more closely than U.S. Pat. No. 6,095,225 to Miller, as the c-shaped channels of the slats fit together in such a way that there is little wasted space between the bodies of the slats. However, the size of the c-shaped channels of these slats still causes the shutter to take up more space than is necessary when in the fully closed position. Furthermore, the shape of the c-shaped channels may cause the shutter to retain water, which can freeze and damage the slats.
Another solution to the problem of compact storage includes the use of slats that do not require large c-shaped channels, as described in U.S. Pat. No. 7,357,171 to Miller, titled “Low-Clearance Shutter Slat.” The slats comprise engaging tracks and receiving tracks that are thinner than the c-shaped channels of U.S. Pat. No. 7,409,980 to Heissenberg. However, the engaging tracks and receiving tracks do not completely minimize the space taken up by the shutter in the fully closed position.
There is a need for shutter slats that minimize the space required for a rolling shutter made up of the slats to be wound up in a fully closed configuration. There is also a need for shutter slats that do not retain water, which can freeze and damage the slats.